It is generally known to provide hand-held garden tools such as pruning shears of the pass-by or anvil-type, wire snips, pliers, and various other cutting implements such as scissors, with a spring mechanism for urging the handles in the "open" position, thereby exposing the jaws or cutters to facilitate operation of the implement by the user. These implements typically include a lock mechanism, functioning against the action of the spring, to maintain the blades in closed position where they are least susceptible to damage and least likely to cause injury to the user when not in use.
Presently, hand-held cutters are locked in the closed position by, for example, a pivoting member secured to one of the cutting jaws, which may be pivoted into abutting relationship with the opposing jaw. Other devices employ a pivoting ratchet mechanism which can be moved from a locked to an unlocked position by the user's thumb. Examples of such pruning implements are described in U.S. Pat. No. 4,156,311, issued on May 29, 1979 to Wallace, et al.; U.S. Pat. No. 4,268,963, issued on May 26, 1981 to Harrison; and U.S. Pat. No. 4,341,016, issued Jul. 27, 1982 to Harrison, et al. As more particularly disclosed in these patents, the locking mechanism comprises a pin slidably positioned in a slot formed in one of the pivoted members to engage a recess or protrusion formed in the other member.
Other locking mechanisms comprise a spring biased stationary pin extending into a mating cavity when the tool is in closed configuration. Examples of such locking means are disclosed in U.S. Pat. No. 3,357,287 issued on Dec. 12, 1967 to Wertepny, and U.S. Pat. No. 4,947,553 issued on Aug. 14, 1990 to Bendickson et al.
It has been found, however, that latching mechanisms of the kind described in these prior art patents have various limitations. For example, certain locking mechanisms of the slidable type do not readily retain their positional adjustment, because the slidable pin tends to slide away from its selected position during normal operation of the implement and may impair normal operation of the tool. On the other hand, other mechanisms which are more reliable are of rather complex construction necessitating several parts, thereby increasing the cost of the tool, and possibly rendering these tools less durable.
Thus, it is desirable to provide an inexpensive lock mechanism for items such as pruning shears or the like which can alleviate the problems associated with conventional latch mechanisms, i.e., which provides a lock having improved positional retention properties, and which requires only a limited number of components of simple configuration to facilitate manufacturing and assembly.